This invention relates generally to a manually actuated dispenser for the metered dosing of fluid from a container to which the dispenser is attached. More particularly, the dispenser has a variable volume pump chamber which is charged upon manually lifting or extending a plunger and is discharged upon manual plunger depression. The charging stroke is limited and may be selective.
The invention is an improvement over U.S. Pat. No. 5,967,377 disclosing a metered dispenser having a variable volume pump chamber which is charged to a measured volume as indicated by a marking on the plunger, and which is discharged by inverting the metered dispenser. The charged volume of the chamber cannot, however, be controlled with any precision since the metering element which defines a pump cylinder is lifted to draw a selected amount of fluid into the chamber as determined by markings on the metered element which indicate predetermined liquid volumes therein. Moreover, the metered dispenser has limited use in that it must be inverted to permit fluid to drain from the metering element by gravity or to be expelled by squeezing the liquid dispenser and/or the metering element. However, if the liquid is viscous, the contents of the pump chamber may not be fully discharged by gravity or even by squeezing the dispenser or the metering element. Besides, the vertically slidable metering element could shift easily in the process of being inverted during discharge whereby additional liquid would fill the metering element inadvertently, thereby affecting the accuracy of the doser.
It is therefore an object of the present invention to provide a metered dispenser which avoids the drawbacks of the known prior art dosers and which is capable of accurately metering liquid product in an upright position.
Another object is to provide a metered dispenser having at least one limit stop for limiting the extractable plunger for suctioning a predetermined volume of product into the pump chamber such that upon full depression of the plunger assembly, an accurate amount of product is dosed through a valve control discharge passage which may be in the form of a spout.
The plunger of the dispenser according to the invention is rotatable amount is central axis and has at least one radial projection which bears against a limit stop when lifted to extract liquid from the container to which the dispenser is mounted. The dispenser may have a plurality of limit stops in stepped formation respectively associated with indicia marked in accordance with the predetermined setting. A lock shoulder cooperating with the radial projection may be provided for locking the plunger in its fully depressed position.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.